Document Type : Research Paper
Authors
Department of Plant Production and Genetics, Razi University
Abstract
Introduction: Salinity stress reduces the yield of agricultural products. Water or soil salinity is caused by the increase in the concentration of soluble salts and minerals in water and soil, which leads to the accumulation of salt in the root area, to the extent that it prevents water absorption and optimal plant growth. In general, tolerance to salinity is important during all stages of plant growth. Seed germination is the first stage of plant growth. Salinity stress reduces the percentage and rate of seed germination and also seedling growth. Crop yield is quantitatively and qualitatively dependent on the percentage, rate and uniformity of seed germination and also seedling growth. In recent years, a lot of attention has been paid to silicon due to its effect in reducing plant damage against some environmental stresses (such as drought, heat, heavy metals, salinity etc.). The studies show that silicon protects the plant against environmental stresses by stimulating growth and increasing the antioxidant enzymes activity. It has also been reported that the silicon is effective in increasing the chlorophyll content, stomatal conductance, photosynthesis rate and the resistance of plants under stressful conditions. Silicon increases the plant tolerance to the salinity by improving photosynthetic activity, increasing the relative selection of K+/Na+, increasing the soluble substances in the xylem, reducing sodium absorption, and mechanical protection against the toxicity of elements. Therefore, a research was carried out with the aim of investigating the effect of the silicon in increasing tolerance to salinity stress in camellia seedlings.
Materials and Methods: A laboratory experiment was carried out in 2021 at Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran. The experiment laid out as a factorial based on a completely randomized design with three replications. The factors were camelina genotypes (Sohail cultivar and Line-84), salinity (four levels 0, -3, -6 and -9 bar) and silicon (five levels of 0, 2, 4, 6 and 8 mM). Salinity stress levels were prepared by different amounts of sodium chloride (NaCl) salt. Silicon factor levels were also prepared by different concentrations of sodium silicate (Na2SiO3). The experiment consisted of 120 petri dishes. Data analysis was done with MSTATC and SAS statistical softwares. Means were compared using Duncan's multiple range test (P≤0.05). Excel software was used to draw figures.
Results and Discussion: The results showed that with the increase in salinity intensity, the growth characteristics and the amount of soluble proteins of camellia seedlings decreased, but the activity of catalase, peroxidase and superoxide dismutase enzymes and the amount of malondialdehyde increased. The lowest activity of catalase was observed under non-salinity conditions (control). But the highest activity of catalase enzyme (104.4 µM/min. mg protein) belonged to the treatment of -9 bar salinity. The use of silicon increased the seedling growth, the amount of soluble proteins, the activity of antioxidant enzymes, and the amount of malondialdehyde in camelina seedlings. The highest germination rate (23.97 seeds/day) was obtained in the treatment of 8 mM silicon. With the increase in silicon concentration, the amount of soluble proteins increased, so that in the 2, 4, 6 and 8 mM treatments, compared to the control treatment, the amount of soluble protein increased by 4, 8, 10.75 and 10.9%, respectively. By increasing the concentration of silicon, the activity rate of catalase enzyme increased. The highest activity rate of peroxidase enzyme (35.38 µM/min. mg protein) was observed in 8 mM silicon, which was significantly different from other treatments. The lowest activity of peroxidase was related to the control treatment. Line-84 had 8.65% higher activity rate of superoxide dismutase than the Sohail cultivar. With increasing salinity stress and silicon concentration, the activity rate of superoxide dismutase increased. On average, in the treatments of 2, 4, 6 and 8 mM silicon, the activity rate of superoxide dismutase was increased 11, 27, 44 and 57%, respectively, compared to the control (without silicon). The highest amount of malondialdehyde (44.42 µM/g fresh weight) was observed in the treatment of 8 mM silicon.
Conclusion: The results of this experiment showed that the application of silicon, by increasing the activity of antioxidant enzymes, reduced the oxidative damage caused by reactive oxygen species and thus protected camellia seedlings against salt stress. In general, it seems that the use of silicon has been effective in reducing the adverse effects of salinity stress on growth and biochemical characteristics of camelina seedlings.
Keywords
Main Subjects
)